Development of an Objective Measure of Temporal Processing in Cochlear Implant Users

This study investigates the use of Schroeder-phase harmonic complexes to develop a cortical auditory evoked potential (CAEP) based objective measure of temporal processing in cochlear implant (CI) users. Recent work from our group has shown that CAEPs can be used to obtain a robust objective measure of spectral resolution in CI users (Lopez Valdes et al., 2014). As speech perception is dependent on both spectral and temporal processing abilities, this research could be complimented by developing an objective measure of temporal processing. Drennan et al. (2008) have shown that Schroeder-phase harmonic complexes can be used in a psychoacoustic paradigm to assess temporal processing in CI users. This study explored the feasibility of using these stimuli to objectively assess temporal processing. Psychoacoustic discrimination of positive and negative Schroeder-phase stimuli were measured in 10 normal hearing (NH) and 6 CI subjects using a four-interval two-alternative forced choice paradigm, using stimuli with fundamental frequencies of 50, 100, 200, 400 and (for NH subjects) 600Hz. Neural discrimination abilities were obtained by recording single-channel EEG from subjects listening to Schroeder-phase complexes of the same fundamental frequencies using an oddball paradigm. Behavioural discrimination scores and neural discrimination abilities were analysed for correlation. Using Schroeder-phase harmonic complexes we were able to obtain CAEPs from all but two subjects. A statistically significant correlation was revealed between the behavioural and neural discrimination abilities in NH subjects. Individual correlation analysis showed strong, but non-significant, correlation in three out of six CI subjects. Due to limitations in the number of subjects tested and the number of stimuli tested for each subject, no final conclusions can be drawn on the feasibility of Schroeder-phase harmonic complexes as an objective measure of temporal processing in CI users. However, it is proposed that Schroeder-phase harmonic complexes have potential to be employed in an objective measure of CI processing.This study investigates the use of Schroeder-phase harmonic complexes to develop a cortical auditory evoked potential (CAEP) based objective measure of temporal processing in cochlear implant (CI) users. Recent work from our group has shown that CAEPs can be used to obtain a robust objective measure of spectral resolution in CI users (Lopez Valdes et al., 2014). As speech perception is dependent on both spectral and temporal processing abilities, this research could be complimented by developing an objective measure of temporal processing. Drennan et al. (2008) have shown that Schroeder-phase harmonic complexes can be used in a psychoacoustic paradigm to assess temporal processing in CI users. This study explored the feasibility of using these stimuli to objectively assess temporal processing. Psychoacoustic discrimination of positive and negative Schroeder-phase stimuli were measured in 10 normal hearing (NH) and 6 CI subjects using a four-interval two-alternative forced choice paradigm, using stimuli with fundamental frequencies of 50, 100, 200, 400 and (for NH subjects) 600Hz. Neural discrimination abilities were obtained by recording single-channel EEG from subjects listening to Schroeder-phase complexes of the same fundamental frequencies using an oddball paradigm. Behavioural discrimination scores and neural discrimination abilities were analysed for correlation. Using Schroeder-phase harmonic complexes we were able to obtain CAEPs from all but two subjects. A statistically significant correlation was revealed between the behavioural and neural discrimination abilities in NH subjects. Individual correlation analysis showed strong, but non-significant, correlation in three out of six CI subjects. Due to limitations in the number of subjects tested and the number of stimuli tested for each subject, no final conclusions can be drawn on the feasibility of Schroeder-phase harmonic complexes as an objective measure of temporal processing in CI users. However, it is proposed that Schroeder-phase harmonic complexes have potential to be employed in an objective measure of CI processing